The present invention relates to a negative pressure control valve for controlling the opening and closing operation of an exhaust gas control valve arranged in an EGR (exhaust gas return) channel communicating an exhaust system with an inlet system of a diesel engine or the like.
Various measures must be taken to treat exhaust gases from a diesel engine mounted on a vehicle as a power source. For instance, it is proposed to form an EGR channel communicating the exhaust system with the inlet system of a diesel engine and to open or close the EGR channel with an EGR valve. The EGR valve is controlled according to the load conditions of the engine.
However, unlike a gasoline engine, the diesel engine does not have a negative pressure source which varies the negative pressure output according to the loading conditions. For this reason, a negative pressure control valve which varies the negative pressure according to the loading conditions must be incorporated so as to control the EGR valve in a diesel engine. Thus, the opening and closing operation of the EGR valve is controlled according to the magnitude of the negative pressure regulated by the negative pressure control valve.